> Interesting, though completely wrong ;)

It couldn't be "completely" wrong since locking the image is a lot
more wrong than not.

> I just pushed a fix. It simply takes evaluating the alarm out of the critical section. Now the error shows just fine.
>
> Don't know how to reproduce your double-firing problem.

The double-firing doesn't seem to happen with your fix.  Thanks!  I'm
really glad to be able to put this lurking spectre bed.